The bond magnet is a permanent magnet obtained by mixing a magnet powder and a resin and then solidifying and molding the resultant mixture via an extrusion molding process, a compression molding process or an injection molding process. Although its performance is worse than that of the sintered magnet, it can be applied to electronic devices such as a motor or various sensors or the like thanks to the great freedom in shape and the good dimensional precision. Especially, the rare earth based bond magnet which has effectively taken advantage of excellent magnetic properties of the rare earth based alloys has been attracting attentions recently. As a well known rare earth based permanent magnet, for example, a Sm—Co based magnet material has been disclosed in Patent Document 1 and a Nd—Fe—B based magnet material has been disclosed in Patent Document 2. In term of the reserves, the price or the like of the raw materials of rare earths, the Nd—Fe—B based material is more widely used than the Sm—Co based material.
The Nd—Fe—B based magnet powder used in the bond magnet can be prepared by producing an amorphous or a submicron microcrystal via a liquid quenching method at first and providing a heat treatment followed by a pulverization process, as disclosed in Reference 2, wherein, the heat treatment mainly aims to control the structure of the amorphous or submicron crystal and the pulverization process provides micron to submicron crystals.